Autoimmune Thyroid Disease in the United States: Population Prevalence, Diagnosis Rates, and Trends

Considerable literature regarding autoimmune thyroid disease (AITD) has been published, but population-based prevalence estimates for US AITD are lacking.

To define the US population burden of AITD, its prevalence, the relative proportions of diagnosed and undiagnosed cases, and trends over time.

Nationally representative population-based data from the cross-sectional US National Health and Nutrition Examination Survey (NHANES) were used. The most recent NHANES thyroid data for the survey years 1988-1994 (n = 15 313) and the 2007-2012 (n = 8775) were analyzed to estimate adult AITD prevalence stratified by diagnostic status, age, and sex. Prevalence trends over time and the number of affected adults were also estimated.

US AITD population prevalences were 5.2% in 1988-1994 and 5.3% in 2007-2012. In 1988-1994 AITD had only a 37% diagnosis rate, whereas the rate was 57% in 2007-2012. There was a 2-fold higher prevalence of AITD in women compared to men: 6.8% vs 3.2% in 1988-1994 and 7.7% vs 2.7% in the 2007-2012 survey data. Over time, women's diagnosis rates increased from 41% to 64%; however, men's rates remained low (29% to 36%) as did rates in younger adults ages 20 to 39 years (39% to 36%).

In the most recent data, an estimated 11.6 million US adults have AITD, 8.8 million women and 2.8 million men. AITD prevalence rates were stable over time; however, the US burden of undiagnosed cases remains substantial. One third of women and 64% of men and younger adults remained undiagnosed, an estimated 2.5 million women, 1.6 million men, and 1.3 million younger adults.